I ran 235/80R17's on my 2500 for several years. Nothing wrong with that size. I know they are both technically called 235 width, but in my experience, a 235/80R17 is a little wider than a 235/85R16 of the same tread. End result is that the 17" version looks a little less skinny in many of the sizes.
FWIW, I think it's a great size for many half ton trucks, and I'll second the 245/75R17 as an additional alternative size. Both offer additional ground clearance without the drag of a significantly taller or wider tire. Properly aired down, you have nothing to fear in sand or other soft surfaces, and a narrower tire on stock wheels will produce less rubbing issues than a wider tire on stock or aftermarket wheels. They also do better on snowy roads, or in really heavy rain, vs. a wider tire of the same tread.
A few pics in my 2500 thread show the 235's on white wheels. (Bottom of 2nd page) My best mileage numbers were recorded with those tires. Many people complain about the ride quality of LT tires on a light truck, but I'm running E rated LT's on our Comanche and my Jeep, and running them at proper pressures, they ride about the same to me. (IE, around what your door sticker says, not at the "Max inflation pressure" listed on the tire.)
And the 255 size is 255/80R17. It's about an inch taller, and an inch wider. I'm running those on my truck and jeep now, and I like that size too, but they are taller, wider, heavier, and more expensive. Everything is a tradeoff.
